Low-pressure gaseous discharge lamp with internally mounted recombination structure



Dec. 8, 1964 v. L. PLAGGE 3,160,775

LOW-PRESSURE GASEOUS DISCHARGE LAMP WITH INTERNALLY MOUNTED RECOMBINATION STRUCTURE Filed March 22, 1962 INVENTOR. VERA/0N L PL/IG'GE.

United States Patent "ice LOW-PRESSURE GASEOUS DESQHARGE LAMP WlTH INTERNALLY MOUNTED REQQMELNA- TIDN STRUCTURE Vernon L. Piagge, East Grange, Nl, assignor to Westinghouse Electric Corporation, East Pittsburgh, 9a., a corporation of Pennsylvania Filed Mar. 22,1952, er. No. 181,592 11 Ulaims. ((Il. 313) This invention relates to electric discharge devices and, more particularly, to fluorescent lamps and means for mounting an elongated member therein.

' It has recently been discovered that the loading per unit length, and hence the light output, of low-pressure gaseous discharge devices such as fluorescent lamps and the like can be increased without decreasing their eh'iciency by providing a region within the discharge where electrons and positive ions can recombine. It has also been found that such a region can beestablished by placing an elongated member within the discharge space which provides a surface at whichthe desired recombination will occur.

The loss of electrons and ions through the recombination process decreases the diffusion length of the discharge and increases the electron temperature which, in turn, increases the loading per unit of lamp length without causing an attendant decrease in efiiciency.

Experience has shown that thethickness of the elongated member must be kept very small compared to its surface area, otherwise the free passage of the discharge through the lamp will be obstructed and the current density per unit of cross-sectional area will be increased. When this occurs both the electron temperature and the lamp efiiciency decrease.

Preferably, a slender glass rod is mounted within the I lamp between the electrodes and in substantial alignment with the envelope axis. The rod is thus suspended in the center of the discharge and provides a recombination surface in the region where the electron and ion concentration is greatest resulting in an optimum increase in the electron temperature and the lamp loading. An axial rod highly-loaded fluorescent lamp designed in accordance with these principles is disclosed and claimed in copending US. application Serial No. 112,071 of D. A. Larson and P. I. Walsh, filed May 23, 1961, and owned by the assignee of the present invention.

The manufacture of such axial-rod fluorescent lamps has presented a structural problem in that it is difilcult to suspend the rod within the envelope withoutobstructing the discharge path. Mounting the rod in the proper position within the envelope and in a manner suchthat it will withstand the mechanical shocks encountered during handling and shipping of the lamps further complicates the problem.

With the foregoing in mind, it is the general object of this invention to provide an'electric discharge device that achieved in accordance with this invention by supporting the glass rod within the envelope by means of vitreous struts that are sealed to the inner surface of the envelope. In the preferred embodiment, a plurality of glass rods are mounted in end-to-end relationship within the V envelope by bending the ends of the rods to form the struts, and then sealing these struts to the envelope wall.

Alternatively, a single rod of sufiicient length is suspended within the envelope and the discharge space by means of a plurality of spaced struts of vitreous material that are sealed to the inner. surfaceof the envelope and joined to the'rod.

In each case, the unsupported lengths of the rod or rods are such that they will withstand the impacts and vibration normally encountered during shipping and bandling. A very convenient method for sealing the supporting struts to the inner wall of. the envelope from a posi-.

tion located outside the envelope is also provided.

A better understanding of the invention will be obtained by referring to the accompanying drawing, wherein:

FIGURE 1 is an elevational view of a highly-loaded fluorescent lamp incorporating the rod structure of this invention, portions of the envelope being removed to afford a clearer view of the lamp interior;

FIGURE 2 is an enlarged'sectional view of a portion of the lamp shown in FIGURE 1;

.FIGURE 3 isan elevational view of one of the rod.

elements shown in the preceding figures;

FIGURE 4 is a view corresponding to FIGURE 2, but

illustrates an alternative embodiment; V

FIGURES 5 and 6 are cross-sectional views through the lamp along the reference lines VV and Vl-VI,

respectively, of FIGURE 2;

FIGURE 7 is a cross-sectional view through a typical highly-loadedfiuorescent lamp provided with a coaxial rod illustrating the character of the discharge that occurs With specific referenceto the drawing, in FIGURE 1 there is shown a watt highly-loadedfluorescent lamp 19 that incorporates the rod structure of this invention. The lamp is approximately 4 foot long and consists of the usual tubular light-transmitting envelope 12 having a mount 14 and an associated electrode 16 sealed into each of its ends. The envelope contains the usual charge of mercury. and a suitableionizable starting gas such as argon, neon, krypton, etc., or mixtures thereof; Inthis particular example the envelope is of the'so-called T17 variety and thus has a diameter of 2 /8". A heat-deflecting disc 15 is attached to each of the electrode mounts to provide a cooling chamber at each end of the lamp which maintains the mercury vapor pressure at the optimum value in the well known manner. A base member 18 is attached to each end of theenvelope to facilitate mounting the lamp in its fixture and connecting it to .a power supply. The inner surface of the envelope is coated with a suitable UV-responsive phosphor 13 in the customary manner.

The Invention Suspended within the discharge space between the elec-.. trodes 16, in accordance 'with this invention, are a plurality of elongated vitreous members such as glass rods 20. As shown in FIGURE 1, the rods are preferably mounted in end-to-end relationship with one another and extend along the envelopeaxis for substantially the entire length of the discharge space so as to eiiect the optimum reduction in the diffusion length of the discharge'and increase in lamp loading, in accordance with the teachings of the aforementioned copending US. application Serial No.

Patented Dec. 8, 19641 so that the alternative lamp embodiment 16a is identical from a functional standpoint with the preferred lamp embodiment described previously.

It will be appreciated from the foregoing that the objects of the invention have been attained by providing an arrangement for conveniently mounting an elongated fragile rod in a predetermined position within a fluorescent lamp or the like without materially obstructing the discharge space or weakening the lamp. Moreover, the configuration of the short rods employed in accordance with the preferred embodiment is such that the rods can be easily produced on a mass production basis with a minimum of cutting and shaping operations.

While several embodiments have been illustrated and described in detail, various structural and procedural modifications can be made without departing from the spirit and scope of this invention. For example, both ends of the short rods can be bent to provide strut segments, or a single strut located intermediate the ends rather than at one end of the rods can be used.

I claim:

1. In an electric discharge device having an elongated envelope that contains a pair of spaced electrodes located proximate the ends of said envelope, the combination of a substantially rigid rod-like member located in and extending longitudinally of said envelope and the discharge space between said electrodes, and means suspending said member in a predetermined region of the discharge space remote from the envelope walls and remote from said pair of electrodes comprising at least one strut that extends transversely of the discharge space and is joined to and integral with said rod-like member and the inner surface of said envelope.

2. The combination in an electric discharge device of a rod-like member and a support strut as set forth in claim 1 wherein said strut comprises a vitreous element that is sealed to the inner surface of said envelope.

3. In a UV-generating device having a vitreous envelope of tubular configuration that contains an ionizable medium and a pair of electrodes located proximate its ends, the combination of a substantially straight vitreous rod extending longitudinally of said envelope and the discharge space between said electrodes, and a vitreous strut sealed to the inner surface of said envelope and integrally joined to said rod, said strut extending transversely of the discharge space and being of such length that said rod is spaced from the envelope walls and sus-' pended solely by means of said strut in a predetermined region of the discharge space between said pairs of electrodes.

4. The combination in a UV-generating device of a axis of said envelope and at a location therein remote rom and between'said pair of electrodes.

6. The combination in a fluorescent lamp of a glass rod and support strut as set forth in claim 5 wherein said strut comprises a bent end portion of said rod, and said strut and rod are both coated with UV-responsive phosphor.

7. A fluorescent lamp adapted for operation at a loadingrof about 25 watts per foot comprising, a tubular envelope of vitreous material, an electrode disposed at each end of said envelope, a plurality of relatively short vitreous rods arranged in end-to-end relationship within said envelope and extending longitudinally thereof and the discharge space between said electrodes, and a transverse strut integrally joined to each of said rods and sealed to the inner surface of said envelope, said struts being of such length and so disposed that said rods are substantially aligned with one another and with the axis of said envelope and are suspended within the discharge space at a location remote from both of said electrodes.

8. A fluorescent lamp as set forth'in claim 7 wherein each of said rods are of circular cross-section and substantially uniform diameter throughout their length, and said struts comprise bent end segments of the respective rods.

9. A fluorescent lamp as set forth in claim 8 wherein said struts are joined to the respective rods by a bend having a radius of curvature greater than about twice the rod diameter.

10. A fluorescent lamp comprising, a tubular glass envelope, an electrode sealed within each end of said envelope, a substantially straight and rigid rod-like member within said envelope extending longitudinally thereof and along a major portion of the discharge space between said electrodes, and a plurality of transversely extending struts of vitreous material sealed to the inner surface of said envelope at intervals along the discharge path and suspending said rod-like member .in substantially coaxial relationship with said envelope at a location therein remote from and between said electrodes.

11. A fluorescent lamp having an overall length of approximately four feet comprising, a tubular glass envelope approximately 2% inches in diameter, a thermionic electrode sealed into each end of said envelope, six glass rods disposed in end-to-end relationship within said envelope and extending longitudinally of the discharge space between said electrodes, each of said rods having an overall length of approximately 6 /2 inches and the References Cited in the file of this patent UNITED STATES PATENTS 834,172 Steinmetz Oct. 23, 1906 2,363,070 Lemmers Nov. 21, 1944 2,635,391 Essig Apr. 21, 1953 

1. IN AN ELECTRIC DISCHARGE DEVICE HAVING AN ELONGATED ENVELOPE THAT CONTAINS A PAIR OF SPACED ELECTRODES LOCATED PROXIMATE THE ENDS OF SAID ENVELOPE, THE COMBINATION OF A SUBSTANTIALLY RIGID ROD-LIKE MEMBER LOCATED IN AND EXTENDING LONGITUDINALLY OF SAID ENVELOPE AND THE DISCHARGE SPACE BETWEEN SAID ELECTRODES, AND MEANS SUSPENDING SAID MEMBER IN A PREDETERMINED REGION OF THE DISCHARGE SPACE REMOTE FROM THE ENVELOPE WALLS AND REMOTE FROM SAID PAIR OF ELECTRODES COMPRISING AT LEAST ONE STRUT THAT EXTENDS TRANSVERSELY OF THE DISCHARGE SPACE AND IS JOINED TO AND INTEGRAL WITH SAID ROD-LIKE MEMBER AND THE INNER SURFACE OF SAID ENVELOPE. 